STORYLINE:

A suspected suicide bomber detonated an explosive Friday in front of the U.S. Embassy in Ankara, killing himself and a guard at the entrance gate, officials said.

U.S. Ambassador Francis Ricciardione told reporters that a Turkish citizen was also wounded in the 1:15 p.m. blast in the Turkish capital.

There was no immediate claim of responsibility, but both Kurdish rebels and Islamic militants are active in Turkey.

The bomb appeared to have exploded inside the security checkpoint at the side entrance to the embassy, but did not damage the inside of the embassy itself.

TV footage showed the embassy door blown off its hinges. The windows of nearby businesses were also shattered by the power of the blast, and debris littered the ground and across the road.

Police swarmed the area and immediately cordoned it off and several ambulances were dispatched.

An AP journalist saw one woman who appeared to be seriously injured being carried into an ambulance but a hospital official said she was "not in critical condition." On its website, the Hurriyet newspaper identified the woman as Didem Tuncay, a television journalist who it said was at the embassy to get a U.S. visa.

The embassy building is heavily protected and located near several other embassies, including that of Germany and France. Hurriyet newspaper said staff at the embassy took shelter in "safe room" inside the compound soon after the explosion.

Phones were not being answered at the embassy later Friday.

Police examined security cameras around the embassy and identified two people who could have been the suicide bomber, a police official said, speaking on condition of anonymity in line with government rules.

In a statement, the U.S. Embassy thanked Turkey for "its solidarity and outrage over the incident."

Kurdish rebels who are fighting for autonomy in the Kurdish-dominated southeast have dramatically stepped up attacks in Turkey over the last year. The United States considers the Kurdistan Workers Party, or PKK, a terrorist organization and has helped Turkey in its battle against the group. But the group has not attacked U.S. targets in its nearly 30-year insurgency.

Homegrown Islamic militants tied to al-Qaida have carried out suicide bombings in Istanbul, Turkey's bustling commercial center. In a 2003 attack on the British consulate, a suspected Islamic militant rammed an explosive-laden pickup truck into the main gate, killing 58 people, including the British consul-general.